BOGOTA, Colombia — Alba Luz Florez, a secret agent with Colombia’s central spy agency, recalled preparing diligently for her mission. At first, she was told only that it was a matter of national security.

She left her family for a safe house and took on a new identity. She underwent three months of intense training on how to develop informants. Then she and planners in the intelligence agency mapped out every step of an operation that called on her to infiltrate the Colombian Supreme Court in the search of evidence linking its justices with the criminal underworld.

“Everything I could learn about the court was of utmost importance to the agency,” Florez, 33, said in an interview with The Washington Post.

Florez said she never questioned the motivation behind the operation, which prosecutors now say was designed to cripple the court’s investigation of corrupt congressmen, most of them allies of then-President Alvaro Uribe. Indeed, the intelligence agency — the Department of Administrative Security, or DAS — was under the control of the president.

“You have a mission, and since it is legitimate, it is legal,” said Florez, who is now cooperating with prosecutors. “I was happy to be able to do the job the institution was asking me to do.”

Her operation, carried out from 2007 to 2009, was not only illegal but, according to Colombia’s attorney general’s office, designed to find incriminating evidence on judges and debilitate their investigation of the president’s congressional allies. The ensuing scandal has led to criminal investigations against Uribe’s top advisers and ensnared the former president himself, who served from 2002 to 2010.

A close U.S. ally in the war against drug trafficking, Uribe’s conduct is now under investigation by a special congressional commission. He denies giving orders to infiltrate the court.

Prosecutors say that DAS’s managers and agents participated in a series of illegal spying operations that over much of the past decade targeted hundreds of Colombians, including opposition politicians, journalists, human rights groups and even U.N. officials. Phones were tapped, agents followed the children of government opponents, and extensive dossiers on dozens of people were put together, according to investigators.

But it was the infiltration of the Supreme Court, an operation called Stairway, that has most astonished Colombians.

Colombia’s Mata Hari

The face of Stairway is Florez, who is officially listed in DAS documents as Agent Y66. To those she met at the court, she had another name: Samantha Rojas. To the Colombian press, she has become “Mata Hari,” the agent whose wholesome looks and mild manner made her well suited to recruiting informants.

She started her work, in fact, by renewing a relationship with an old flame, a policeman who worked in the government’s security apparatus and helped her make the initial contacts in the bunkerlike building where the court is housed. With his help, she set about meeting cleaning ladies, chauffeurs, bodyguards — people she eventually recruited to help her “penetrate” the court, as she put it.

The driver for the court’s star investigative magistrate, Ivan Velasquez, was crucial, she recalled. He had access to documents that DAS superiors and officials in the president’s office wanted to see, said Florez and her handler, William Romero, who had headed the DAS unit that oversees informants and is now cooperating with prosecutors. To win the driver over, Florez said, she had to learn about his weaknesses.

“I knew absolutely everything about his family, his children, what he liked and what he needed,” she said.

She found out that the chauffeur had a growing brood of children and was short of cash. He had also been in the army. Florez said she offered him money and appealed to his patriotism, explaining that there were “irregularities” in the court that could damage Uribe, a popular president beloved by many Colombians.

“I told him, ‘Let’s do this for the president,’ ” she said.

Another court worker, Blanca Maldonado, remembered how Florez also sweet-talked her by stressing that her cooperation with the spying operation would benefit Uribe.

“From the beginning, she indicated that she belonged to a special DAS program collecting information for Dr. Uribe,” Maldonado, who was the “coffee lady” who served the court’s justices, said in a deposition revealed by Semana magazine. “She asked me if I did not feel proud working for him, Dr. Uribe, and I just smiled.”

Florez also won over Maldonado and the cleaning crew by offering hundreds of dollars in cash a month. Their main job was to plant tiny microphones in a court chamber where judges held private conversations.

“Little by little,” Florez said, “I won them over. I conquered them.”

‘This is deplorable’

The law firm representing Uribe and Bernardo Moreno, the jailed former chief of staff to the president, say that Florez’s infiltration was her own doing and that of a small group of rogue DAS agents.

“This is deplorable. It is an embarrassment for Colombia,” said David Espinosa, one of the lawyers in the firm. “The question is, did the official do it on her own? Who gave her the order? She cannot say she got the order from Dr. Bernardo Moreno nor anyone in the presidential palace.”

Florez’s superior, Romero, said that two high-level DAS officials — the former director of intelligence, Fernando Tabares, and the director of the agency, Maria Pilar Hurtado — made clear the orders came from the president’s office. Romero’s superiors, in fact, were under so much pressure from above that they ordered him to launch Stairway as soon as possible.

“That is when I gave the mission to Alba,” Romero said. “I told her, the target is the Supreme Court and the order comes from the president. She complies because it is a privilege.”

Florez said a priority became obtaining the archives of the court’s investigations of the congressmen accused of ties to the paramilitary warlords who then controlled much of northern Colombia, a scandal known as para-politica.

“They wanted to know how the cases were coming,” she said of her superiors, especially the investigation the court was carrying out against the president’s cousin, Mario Uribe, then a senator.

Suddenly shut down

From the court, Florez and Romero said they managed to obtain case loads on up to 30 congressmen, which were promptly handed over to the presidency. She had to turn in four reports a month. Those reports, along with court documents and the transcripts from the surreptitiously taped conversations of judges, sometimes amounted to 1,000 pages a month.

Velasquez, the court’s lead investigator, said he had never imagined outsiders would know so much about his investigations, noting that his small office was bugged.

“Here I talk with all kind of people, with lawyers, with eventual witnesses that come to inform, people who know things and want to collaborate,” he said.

Florez said she never asked what became of her reports. She said she only heard from Romero that DAS superiors were pleased with her work.

Then, just as suddenly as it began, Operation Stairway was abruptly shut down. Romero said he was then ordered to shred documents.

The DAS never found ties between the court’s magistrates and criminal figures.

But the court’s investigations into criminal activity by lawmakers has led to nearly 30 convictions, including that of the president’s cousin, the former senator, who was sentenced earlier this year to eight years in prison. Up to 20 other lawmakers are either on trial or under investigation.

Maldonado is also under investigation. In her deposition, she lamented her role, saying she had allowed Florez to make her think that the court’s magistrates were conspiring against Uribe.

“I ask for their forgiveness,” she said, “and say to them that because of ignorance or stupidity, I did something very low.”

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